The proposed study aims to develop a practical clinical approach to evaluating hypertensive children using the degree of activity of the renin angiotensin system as the focal point upon which to base additional studies. This will be accomplished by developing in normal children criteria by which renin activity may be defined as being normal, low, or high. The activity of the renin angiotensin system will be defined by obtaining 24-hour urine sodiums and 4-hour upright plasma renin activity and defining the acute change in plasma renin activity to the oral administration of a potent diuretic. Similar data will be obtained in hypertensive children and the distribution of various subgroups of essential hypertension defined. Patients with either suppressed or increased renin activity will undergo appropriate additional studies to seek secondary causes of hypertension. The data in the hypertensive children will be compared to age related normals and will also be compared to similar type studies in children and adults and most importantly evaluated in terms of the large amount of prospective data both psychosocial and medical previously accumulated as part of other studies, Philadelphia segment of the National Collaborative Perinatal Center and a currently active, involving their children, Antecedents of adolescent Hypertension. In addition, the relationship of serum uric acid levels rates of execution of uric acid and uric acid clearances will be evaluated in hypertensive children, and compared to values obtained in age related normal children.